Modification of POTA developer
I am form Russia and I use very good Tasma Type-17 film (it is Russian film for aerophoto shooting). The main issue of this film is high contrast, but it has very good grain and tonality. By experience I found the best developer for the film - POTA (phenidone - 1,5 g, sulfite - 30g). But I would like to try sharpness variant of this developer, if it possible. Could you be so kind to say what could I try to add to developer? I would try to add potassium carbonate, but I am afraid for contrast elevation.
I believe Tasma type 17 has ISO 400, is that true? I assume it is similar in contrast to the former tech pan.If that is so, it could be used with H&W Control microfilm developer,that will give higher speed than Pota, it contains carbonate.
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Well you can give the A49 developer (by Calbe, ex-Orwo) a try. A further modification would be adding some pota in further trials.
Thank you, Alan, but my aim is not push the film, but to have more sharpness results, for example, like in diluted 1;100-1:200 Rodinal with keeping little contrast. I tried to push Tasma in Microphen with acceptable result, but it is not the case now.
Originally Posted by Alan Johnson
Do you have a formulation of A49? Google is keeping silent about it...
Originally Posted by AgX
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In some developers where carbonate improves sharpness a speed increase is obtained as well,eg FX-37 in articles section.The carbonate in H&W Control may cause a similar effect, but still improve sharpness while giving normal contrast,the speed increase being a consequence of carbonate addition even if it was not sought after.
As an aero film, isn't it already sharp as hell? IIRC, the aero Panatomic X had something like 400lpm.
As a total guess, I would lean towards a very dilute developer like Rodinal in a stand or reduced agitation regimine.
The Tasma Type 17 has got a resolution of 120 LP/mm.
For high resolution reconnaissance work there were other films.
Thanks for the info. I never was much up to speed on Russian aero filsm! :rolleyes:
Originally Posted by AgX
The Russian government developed several outstanding aerial reconnaissance films as part of their space program in the 1960s and 1970s. It's good to see that some of them are surfacing for civilian use.
Anchell and Troop list several variations of POTA in their "The Film Developing Cookbook." Most were designed to solve some POTA problem with Kodak Technical Pan, including excessive fog and streaking. Here are some examples:
Water (52C) 750 ml
Sodium Sulfite (anh) 10 g
Phenidone 500 mg
Hydroquinone 250 mg
WTM 1 l
This modification is an attempt to optimize POTA for Technical Pan film. Add borax or sodium bicarbonate as desired to control time, contrast, and speed. Develop 11 minutes.
TDLC-101 and TDLC-102 modify POTA by adding a second developing agent (glycin) to stabilize it. The variation also raises the contrast a bit.
Sodium Sulfite (anh) 4 g
Phenidone 100 mg
Glycin 500 mg
Sodium bicarbonate 20 g
Sodiun sulfite (anh) 4 g
Phenidone 250 mg
Glycin 250 mg
Sodium bicarbonate 5 g
Both TDLC-101 and TDLC-102 could be modified by adding 1 to 10 mg of potassium iodide.
Another variation would be to add 50 ml per liter of isopropyl alcohol.
Delagi-8 is said to raise both the speed and the sharpness of Technical Pan compared to POTA development.
Sodium sulfite 25 g
Phenidone 1.4 g
Borax (decahydrate) 2 g
Benzotriazole 0.2% 15 ml
Substitute sodium metaborate for borax to get higher speed and contrast.
Benzotriazole may not be active at low pH and could be eliminated. Potassium
bromide or iodide might also be substituted.